Array Slices and Interior Pointers

[Alex Rønne Petersen]

On 11-12-2012 02:49, Timon Gehr wrote:
> On 12/11/2012 01:04 AM, Alex Rønne Petersen wrote:
>> http://xtzgzorex.wordpress.com/2012/12/11/array-slices-and-interior-pointers/
>>
>>
>>
>> Destroy.
>>
>
> Why does the internal representation have to be the same for a managed
> port and native D? Also, how does the second representation work
> exactly? Not all slices extend to the end of the memory block.

They don't have to be. Ideally it shouldn't even have to matter because 
D code shouldn't make assumptions about it.

And good point. That makes the second variation not useful for VMs that 
don't natively support slicing arrays, so I'll scratch that as a useful 
representation. A representation for a VM would then probably need to be 
{length, base, offset} (which could also work for a native D).

>
> I don't really feel strongly about the memory requirements for slices,
> but 12 / 24 bytes is starting to feel a little bulky. I am not
> intimately familiar with druntime, but OTOH and AFAICS, the additional
> pointer should also allow faster retrieval of the slice's capacity.
> (though the compiler should IMHO implement specific optimizations for ~=
> in loops anyway.)

Some optimizations can probably be done when the base pointer is known.

-- 
Alex Rønne Petersen
alex at lycus.org
http://lycus.org